Two issues that arise after reading this article is that not all states monitor for nitrates in the drinking water, and this is something that needs to be changed, because people should know what they are drinking. The other issue is that even when state governments do monitor for nitrates, the findings can be inaccurate.
This article has a lot of information about nitrate levels in drinking water and how it is related to income level, race and location. Residents in a majority of counties across the United States are exposed to potentially unsafe levels of nitrate from drinking water.
It is also vital to note that disparities in drinking water exposures to nitrate are quite common in both rural and urban communities and persist even after accounting for differences in income, age, race/ethnicity, education and other factors.
Many of the disparities are attributed to differences in the percentage of African Americans- and Hispanics- among residents within the same county. In addition to race/ethnicity, disparities may also be associated with location. In one study, nitrate concentrations differed by up to threefold between areas of a county with high rates of poverty and those with low rates of poverty.
Futhermore, Safe Drinking Water Act (SDWA), the organisation that monitors and regulates drinking water quality, has deemed the general population to be exposed to nitrate concentrations in excess of 10 ug/L, the level where all health effects from ingestion, inhalation and skin contact would be expected to occur.
In most cases, nitrate levels were found in excess of that level for both African Americans and Hispanics, but not as large a disparity between African American and white residents.
The SDWA limits states to setting a maximum nitrate concentration in drinking water of 10 ug/L.